Three dimensional digitizer using multiple methods

ABSTRACT

A method and apparatus capable of using two or more capture methods to create three-dimensional representations of a target captured. Elements of the three-dimensional digital representation generated from the plural capture method are combined to yield a single digital three-dimensional representation having improved quality.

This is a divisional of Ser. No. 09/660,809 filed on Sep. 13, 2000 nowU.S. Pat. No. 6,639,684 entitled DIGITIZER USING INTENSITY GRADIENT TOIMAGE FEATURES OF THREE-DIMENSIONAL OBJECTS.

BACKGROUND

1. Field of the Invention

The invention relates to an image capture device. More specifically, theinvention relates to a low-cost three-dimensional digitizer.

2. Background

There are four broad categories of non-contact three-dimensionaldigitizers. The first category is referred to as silhouette digitizersbecause the imaging device repeatedly takes the silhouette of the objectas the object is rotated before the imaging device or the imaging deviceis rotated about the object. This type of digitizer is relativelyineffective at dealing with concavities in a three-dimensional objectbecause the silhouette is unchanged by the concavity.

The second category is timing digitizers. Timing digitizers use a signalsource such as a radar source. By determining the amount of timerequired for the signal to bounce back from the different points on thetarget object, surface features of the object are revealed. However,such digitizing methods are extremely expensive to implement.

A third category is projected pattern digitizers, in which a pattern ofsome sort is projected onto the object to be digitized and thedimensions of the object are determined from the interaction of thepattern with the object. Projected pattern digitizers fall into threemain subcategories. The subcategories include contour digitizers whichuse spatial distortion from a projected pattern of contour lines todetermine surface features of a three-dimensional object. A nextsubcategory is interference projected pattern digitizers, which use twosources and then based on the localized interference pattern of the twosources, determine the surface features of the three-dimensional objectto be digitized. A third subcategory is referred to as color projectedpattern digitizers because this category uses a projected color patternand resulting color gradients to determine relevant information aboutthe object to be digitized.

A final broad category is stereoscopic digitizers which employ multiplecameras to capture images of the object from different angles. From thepicture, such systems perform feature identification. Then a correlationbetween the features in the different pictures is established to yieldthree-dimensional data.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

FIG. 1 is a block diagram of a system of one embodiment of theinvention.

FIG. 2 is a block diagram of a control subsystem of one embodiment ofthe invention.

FIG. 3 is a perspective view of a digitizer of one embodiment of theinvention.

FIG. 4 is a perspective view of a digitizer of one embodiment of theinvention with a portion of the housing removed.

FIG. 5 is a rear perspective view of one embodiment of the digitizerwith a portion of the housing and base removed.

FIG. 6 is a bottom perspective view of a digitizer of one embodiment ofthe invention using an alternative optics arrangement.

FIG. 7 is a top perspective view of the embodiment of the digitizer ofFIG. 6.

FIG. 8 a is an additional alternative embodiment of a digitizer of oneembodiment of the invention.

FIG. 8 b is a sectional perspective view of a portion of one embodimentof the invention.

FIG. 9 is a perspective view of a magnetic drive unit of one embodimentof the invention.

FIGS. 10 a–c are perspective views of components of a magnetic drive andreflector assembly of another embodiment of the invention.

FIG. 11 is a perspective view of a projection subassembly of oneembodiment of the invention.

FIG. 12 a is a sectional perspective view of an inclinometer disclosedwithin the camera case.

FIG. 12 b is a perspective view of the inclinometer positioned relativeto the image sensing array.

FIG. 13 a is a schematic diagram of a system of one embodiment of theinvention at first mode of operation.

FIG. 13 b is a schematic diagram of a macro lens solution to imagingsmall objects in one embodiment of the invention.

FIG. 13 c is a schematic diagram of an alternative macro lens solution.

FIG. 14 is a prospective view of an imaging assembly of one embodimentof the invention.

FIG. 15 a is a diagram of a lens/aperture assembly of one embodiment ofthe invention.

FIG. 15 b is an exploded view of the assembly of FIG. 15 a.

DETAILED DESCRIPTION

The system operates on the principle that depth data for athree-dimensional object may be calculated from an intensity differenceresulting from an intensity gradient projected on the object. Existingimage sensing arrays (ISAs) such as linear charge coupled device (CCD)sensors can detect illumination intensity to a high degree of accuracy.Based on this principle, if a light source is placed in fixed relationto the ISA such that the projected light forms an angle with the focalline of the ISA, and a gradient slide, for example, going from dark tolight, from left to right, is interposed between the light source andthe object, features of the object closer to the ISA are illuminated bygreater intensity light than those features further away. Thus, the ISAcaptures a stripe of the object in which different intensities representdifferent depths of the object in that focal zone. This generalprinciple works well for uniformly colored objects imaged in anotherwise dark environment, but different coloring and ambient lightconditions may cause misinterpretations of the intensity data. However,if the ISA images the same stripe of the object under ambient conditions(e.g., when the light source is not illuminating the object within thefocal zone) and images again when the object is illuminated by a uniformlight (e.g., with no gradient (flat gradient)), these possiblemisinterpretations can be avoided.

Particularly, the ratio V_(G1)−V_(A)/V_(G2)−V_(A) yields a differentialthat can be mapped to depth of the object. In the differential, V_(G1)is the value from the ISA at a point resulting from the gradientexposure, V_(A) is the value from the ambient exposure at that point,and V_(G2) is the value at the point from a second gradient exposuresuch as the uniform light (flat gradient) or a second gradient createdas described further below. The differential is computed for each pointin the focal zone. Moreover, this differential also normalizes theeffect of color variations and ambient light conditions. Notably, thedifferential is also substantially independent of intensity of the lightsource. Unfortunately, as a practical matter, changing slides and/orturning the light source on and off rapidly enough to permitdigitization of many possible target objects is both expensive andproblematic.

However, by taking advantage of the fact that the ISA integrates overtime, the same effect may be created mechanically using a shutter whichcauses 0% to 100% of the light to illuminate the target object withinthe focal zone during the cycle. Moreover, by overdriving the shutter,the white light condition and ambient condition, can be created.Specifically, if the imaging time of the CCD is 5 milliseconds, in aninitial 5 milliseconds the shutter does not impinge on the light source,thereby allowing the imaging sensing array to image the fullyilluminated object. The next 5 milliseconds, the shutter passes from 0to 100% blockage of the light, thereby creating the intensity gradientwithin the focal zone. During the next 5 milliseconds, the shuttercontinues to drive so that the light is entirely blocked and the ambientcondition image is obtained. The processing of each of these images(including the creation of the differential) may be offloaded to anattached host as discussed in greater detail below.

An intensity gradient may alternatively be created by sweeping the lightthrough the focal zone. For example, by sweeping a light stripe fromleft to right through the focal zone, the ambient light image may becaptured before the light enters the zone. A first gradient is capturedfrom the first entry of the light into the zone until the light isentirely within the zone. A second gradient is captured as a lighttranslates out of the zone to the right. The second gradient is theopposite of the first gradient and is not flat as in the fullyilluminated case. An analogous set of images may be captured as thelight sweeps back from left to right. One advantage of sweeping thelight is that two gradients are generated as the light moves from rightto left and two gradients are generated as the light moves from left toright. Thus, the sweeping can be performed at half speed without areduction in imaging performance.

The differential may take the same form as discussed above.Alternatively, the differential may be computed as X₁/(X₁+X₂), whereX₁=V_(G1)−V_(A) and X₂=V_(G2)−V_(A). To reduce noise sensitivity, thelarger magnitude gradient should be selected for the numerator of theratio. Color intensity is given by X₁+X₂.

It is possible to calculate the depth data directly from the intensityinformation. However, the speed and processing power required is reducedwhen a lookup table (LUT) based on a prior calibration is employed toderive depth data based on the differentials. Accordingly, theembodiment of the invention maintains a LUT and indexes into the LUTbased on the differential.

FIG. 1 is a block diagram of a system of one embodiment of theinvention. A digitizer 70 is coupled to a host node 50. This couplingmay be by a bus 60 such as the Universal Serial Bus (USB), IEEE 1394bus, or any other suitable data transfer system. It is also within thescope and contemplation of the invention for the digitizer tocommunicate with the host mode via a wireless interconnection. Host node50 may be a personal computer, a work station, an internet appliance, orany other device that provides sufficient intelligence and processingpower to render images from the data obtained by the ISA. The digitizer70 captures image data and may forward it to the host node 50 forrendering. In this way, the processing on the digitizer 70 may belimited, permitting lower cost construction.

The digitizer 70 includes a projector to project a stripe of white lightthrough a projection window 74 onto a remote object such as a person 82on a turntable 80 remote from the digitizer. The digitizer also containsan image sensing array (ISA) aligned with an image capture window 76which captures the image of the object 82 within a focal zone. In oneembodiment, the ISA is a linear charge coupled device (CCD) orcomplementary metal oxide semiconductor (CMOS) sensor, and the focalzone is a line on the target object. In some embodiments, the digitizerincludes a base 72 about which the upper unit, including the projectorand the ISA, can rotate in either direction. This permits the focal lineto be swept back and forth across a target object through an arc. Thissweeping reduces the loss of detail in the captured image that resultsfrom shadowing on the object from the perspective of an immobile focalline. The digitizer 70 also includes a wireless interface to communicatewith a turntable 80 via a wireless link 84.

Turntable 80 may be the type described in co-pending applicationentitled Wireless Turntable, Ser. No. 09/660810, assigned to theassignee of the instant application. Via wireless link 84, the digitizersends commands to the turntable 80 and receives from the turntableindications of the angular position of the turntable surface relative toa home position. When the digitizer is activated, it searches for theturntable 80 by sending a signal to which the turntable 80 is requiredto respond. If the turntable responds, the digitizer looks for apredetermined pattern that is expected to be present on the turntablesurface. For example, the pattern may be concentric circles on theturntable surface. In such case, based on the image captured, thedigitizer can both find the turntable and determine its distance fromthe digitizer. Then after the response is received, the digitizer sendsa “go home” signal to the turntable. In some embodiments, the digitizersends acceleration and rotation profiles to the turntable to control itsrotation. Each profile may be retained in firmware on the digitizer ordownloaded from host node 50.

Generally speaking, the projection portion of the digitizer 70 isretained in fixed relation to the imaging portion. The projectionportion produces a light stripe as noted previously on the object 82. Byeither sweeping the light stripe back and forth through the focal lineor by mechanically blocking the stripe at a known rate, the intensitygradient can be created. In one embodiment, the blocking is from 0% to100% during a cycle. Because the ISA integrates the illumination overtime, the outline of a three-dimensional surface is reflected in thedata captured by the ISA. This is because protruding features willremain illuminated longer. Accordingly, more photons are captured by theISA corresponding to those features. After repeating this process onestripe at a time as the object is rotated by turntable 80 or through thecourse of sweeping the entire digitizer back and forth as it rotatesabout the base, cost effective three-dimensional imaging is effected.The digitizer may also be used to capture high resolution scans of twodimensional objects by sweeping back and forth across the object. Thisfeature is particularly desirable in the context of digitizing works ofart.

FIG. 2 is a block diagram of the control subsystem of one embodiment ofthe invention. The processor 304 is coupled to a random access memory(RAM) 312 and an erasable programmable read only memory (EPROM) 308. TheEPROM 308 contains firmware necessary for booting the processor and may,for example, include rotation profiles and the command set for thewireless turntable. The wireless interface 302 is used by the processor304 to signal the wireless turntable. The processor 304 is coupled tothe ISA 300 which sends image data to the processor for storage in theRAM 312 or to be forwarded to the host over USB or other suitableconnection. The processor 304 also controls the drive motor 306 toaffect sweeping rotation of the digitizer. The processor 304 alsocontrols projection subsystem 314, particularly whether the light sourceis on or off, as well as in certain embodiments, the activation anddeactivation of the shuttering or sweeping of the light beam. The samegeneral control structure is employed in the various mechanicallyvarying embodiments of the invention described below.

FIG. 3 is a perspective view of a digitizer of one embodiment of theinvention. A housing 10 is coupled to a base 12. In some embodiments,the coupling between housing 10 and base 12 may be a rotatable coupling,such that the housing 10 projection and imaging units within may berotated axially about base 12. Housing 10 defines a projection window 14and an image capture window 16. In one embodiment, housing 10 is moldedout of ABS. Housings made of other plastics or metal are all are withinthe scope and contemplation of the invention. The material used for thewindows may vary from one embodiment to the next, depending on theoptics employed within the housing.

FIG. 4 shows a perspective view of a digitizer of one embodiment of theinvention with a portion of the housing removed. A mounting plate 18which forms the bottom of the housing serves as the mounting surface formost of the internal components. A motor 42 is also mounted to themounting surface to drive rotation of the assembly about the base 12.The requisite gear assembly may be arranged to reside in the housingand/or the base. A camera case 20 retains a lens in opticalcommunication with an ISA. The camera case 20 prevents ambient lightfrom distorting the image captured by the ISA. Also mounted in a fixedposition relative to where the camera case 20 is a light source 22.Adjacent to the camera case 20 is a circuit board, including a processorand a memory that provide the brains and storage, respectively, for thedigitizer.

A wireless interface is also provided and may signal the turntable (notshown) through the imaging windows. The wireless interface may forexample be an infrared interface or a radio transceiver, either of whichmay employ well understood protocols for sending and receivinginformation from the turntable. In one embodiment, light source 22 maybe a 300 watt halogen tube. A first elliptical reflector 24 is mountedon one side of the light source 22, while a second elliptical reflector26 is mounted on the other side of the light source 22. In this manner,the first elliptical reflector 24 focuses the light from light source 22back on the second elliptical reflector 26, which in turn, focuses alight to a focal point some distance from the light source. In oneembodiment, first elliptical reflector 24 is semi-circular. Mounted atthat focal point is a light homogenizer 28, which in one embodiment ofthe invention, may be polished float glass. The float glass basicallyfunctions as a light pipe that uniformly distributes the intensity suchthat a substantially uniform intensity light stripe exits the terminalside of the float glass.

Coupled to the float glass is a light folding mirror 30, which is usedto fold the light projecting out of the homogenizer 28 on itself. Byfolding the light, a smaller size lens may be employed subsequently tofocus the light on a target object. In one embodiment, the foldingmirror 30 is omitted and a larger lens is used. A lens 34 is mounted tofocus light from the light source through the projection window to alocation remote from the digitizer. An additional mirror or mirrors 36may be employed to ensure optical communication between the light source22 and the lens 34. The lens 34 and other optical component may bemanufactured from various suitable materials known in the art.

A shutter blade 32 is mounted, such that when driven, it will impinge onthe light exiting the homogenizer, such that it varies between blocking0% and 100% of that light from reaching the lens 34. The shutter bladeis mounted to a spider, such as might be found in a conventional stereospeaker, which is driven by an electromagnet 40. In this manner, theshutter can be driven to pass through an entire cycle of 0% to 100%blockage, in a hundredth of a second. Moreover, the spider mechanism hasbeen found to be quite smooth, resulting in minimal mechanicalvibration, which might otherwise have deleterious effects on the imagingof the system. In an alternative embodiment, the shutter may be mountedto a pair of leaf springs and driven by a coil.

FIG. 5 is a rear perspective view of one embodiment of the digitizerwith a portion of the housing and base removed. The housing and itsprojection and imaging subsystems are mounted on a central post 48extending from a floor of base to engage the mounting platform 18 of thehousing. A bronze bushing may be used around the central post to aid inachieving smooth rotation. By using a hollow axial post 48, the overallheight of the unit is reduced as in such an embodiment the light sourcemay be mounted to extend it down within the post 48.

Transformer 54 resides within the base and is used to power the varioussystems of the digitizer. An optical interrupter for 52 is used toidentify where the upper unit is relative to the base as it rotatesabout the axis 48. To effect this, one or more blades are molded tointerrupt the sensor as the upper unit rotates. A USB port 44 isprovided to permit data to be sent back and forth to a host node. Othertype of ports could be used instead or in addition to USB. An AC powerport 46 is similarly provided within the base to provide the power totransformer 54.

FIG. 6 is a bottom perspective view of a digitizer of one embodiment ofthe invention using an alternative optics arrangement. A portion of thecamera case is removed to reveal the image sensing array 100, which inone embodiment of the invention, may be a 5340 pixel linear imagesensor, such as the one available from Toshiba America, Inc. of NewYork, N.Y., available under the part number TCD2558D. The light source122 is mounted within a parabolic reflector 124, which focuses the lightfrom light source 122 onto a curved reflector 126. In one embodiment,the light source 122 is a 150 watt single end halogen bulb. The curvedreflector 126 spreads the light into a light stripe that is thenreflected through the projection window onto the target object at apredetermined distance from the digitizer. The curved reflector 126 maybe moved back and forth to sweep the light stripe through the focal zoneon the target object. The reflectors may be manufactured from plastic orpolished metal. In one embodiment, stamped aluminum is used.

FIG. 7 shows a top perspective view of the embodiment of the digitizerof FIG. 6. The curved reflector 126 can still be seen beneath the lightsource (not shown). Motor 142 drives a gear assembly 152, which engagesdrive gear 154 to permit rotation of the upper unit, including theprojection system (light source and reflectors) and the image sensingarray 100 about the base 112. By rotating about the base, the digitizeris provided with an additional degree of freedom, which facilitatesscanning in some situations, as described in more detail below.

FIG. 8 a shows an additional alternative embodiment of a digitizer ofone embodiment of the invention. Similar to the embodiment discussedwith reference to FIG. 6 and FIG. 7, this embodiment uses parabolicreflector 224 in conjunction with light source 222 to produce aspotlight. However, rather than using a curved reflector (which performsa light spreading function), a flat reflector 226 is employed to reflectthe spot of light to the projection window 214. Projection window 214 ismanufactured from a pane of glass or plastic to have a plurality ofconcave or convex ridges. Each such ridge acts as a lens spreading thelight thereby changing the spot of light to a light stripe which hasrelatively good intensity uniformity from top to bottom. A magneticdrive unit 250 is used to move reflector 226 back and forth to cause thespot of light to move back and forth across the projection window 214and, therefore, the light stripe to move back and forth across in thefocal line of the ISA. It is also within the scope and contemplation ofthe invention to effect the sweeping by moving the light source andparabolic reflector while maintaining the other reflector stationary.

In one embodiment, an IR filtering or hot mirror (not shown) isinterposed between the light source 222 and the reflector 226. A fan maybe introduced between the IR filter and the light source 222 to cool thelight source 222. However, in such an embodiment, partitions may bedesirable such that the housing, in conjunction with the partitions, theIR filter, and the parabolic reflector 224 form a fan enclosure whichprevents turbulence created by the fan from disturbing the regularmovement of reflector 226. The motor 242 is provided to drive gearassembly 252, which in turn drives major gear 254, thereby causing theupper portion of the digitizer including the projection unit and theimaging unit to rotate about the base 212. This permits the digitizer tosweep back and forth while scanning an object. Thus, an object somedistance from the digitizer may be scanned, for example, 90° of theobject at a time, requiring only four rotations by the turntable. In oneembodiment, the gear ratio is 512. Similar motor and gear assemblies maybe used in each of the various above described embodiments. It is, ofcourse, possible for the digitizer to image an object continuallyrotated by the turntable. The sweeping the focal line (even in acontinually rotating environment) also permits features to be moreaccurately identified than would be possible with an immovable focalzone. Particularly, sweeping the focal line reduces inaccuracies due toshadowing.

The electronics board 258 is substantially the same as in the otherembodiments, as is the imaging subsystem. Wireless signaling interface260, which in this embodiment is a infrared signaling interface, signalsthe turntable through the imaging window. An activation switch 262 issupplied on the electronics board 258 to permit the system to beactivated.

FIG. 8 b is a sectional perspective view of a portion of one embodimentof the invention. Gear assembly 252 is mounted on gear box 286. Gear box286 is elastically coupled to the lower unit by bias spring 282. Biasspring 282 biases gear assembly 252 into engagement with major gear 254.Additionally, bias spring 282 biases the shaft 248 to lean in aconsistent direction. This is desirable, because if the shaft were freeto float from side to side, even given quite tight tolerances, thatminor variation at the digitizer may represent a significant deviationeight feet away in the focal zone. Thus, absent some biasing mechanismto ensure consistency in the shaft, risk of lost data is increased.Anti-vibration spring 280 is compressed between washer 290 that moveswith the shaft and bushing 288 that moves with the upper unit. As aresult, anti-vibration spring 280 increases rigidity of the upper unitand prevents vibration and wobble from side to side. Use of these biassprings permits a less expensive bearing with greater tolerances to beused. Power cables 284 are fed through the hollow shaft 248 to providepower to the light source (not shown).

FIG. 9 is a perspective view of a magnetic drive unit of one embodimentof the invention. As previously noted, the reflector 226 is coupled tothe magnetic drive unit 250. Specifically, it is coupled to an arm 276which is able to pivot in a horizontal plane. The distance of pivot iscontrolled to some degree by a pair of spring steel bands 280, whichprovide a restraining force against rotation from a central position. Afirst magnet 270 having a first polarity is positioned on one side ofthe arm 276. A second magnet having the opposite polarity is positionedon another side of arm 276. A coil 274 runs around the arm and betweenthe first and second magnets 270 and 272. When the coil is pulsed withcurrent, the magnets 270 and 272 intermittently apply torque to the arm276. The result is that arm 276 moves back and forth in an arc within ahorizontal plane. Movement of the arm 276 is translated to movement ofthe reflector 226, and consequently, sweeping back and forth with thelight beam reflected thereby. This system employs certain resonanceprinciples to improve energy efficiency such that the power cost ofsweeping the reflector is quite low.

FIGS. 10 a–c show perspective views of components of a magnetic driveand reflector assembly of one embodiment of the invention. The reflectormagnetic drive assembly as shown in FIG. 10 a is similar in manyrespects to that shown in FIG. 9. However, rather than mounting themagnetic drive portion behind the reflector, it is mounted in front andbelow the reflector. Thus, first magnet 370 having a first polarity ispositioned on one side of arm 376, and a second magnet having theopposite polarity is positioned on another side of arm 376. A coil runsaround the arm between first and second magnets 370 and 372. When thecoil is pulsed with current, the magnets 370 and 372 intermittentlyapply a torque to the arm 376. The result is that arm 376 moves back andforth in an arc within a horizontal plane.

Movement of the arm 376 is translated into movement of the reflector326, and consequently, sweeping back and forth of the light beingreflected thereby. The reflector 326 is mounted on a fulcrum post 390.No spring steel bands are provided. Rather, a pair of springs 386 arecoupled at the base of the mirror to provide opposing restraining forcesto cause the mirror to move back and forth in a resonant manner. Thespring constants of springs 386 dictate the resonance frequency, whichtranslates to the sweep rate. This mounting results in smooth consistentlow friction movement of the reflector during operation. In oneembodiment, the springs 386 are selected to yield a resonance frequencyof approximately 50 Hz. A much smaller spring 384 is coupled to fulcrumpost 390 and mounting clip 382. The purpose of spring 384 is merely tohold the reflector into the circular fulcrum member discussed below. Byhaving the springs 386 which dictate the resonance frequency of theapparatus positioned at the bottom of the reflector to be moved, thetorque created by the magnetic attraction and repulsion of the arm 376is applied significantly more proximately to those springs 386 than werethey at the top of the reflector, thereby improving system efficiency.Additionally, a light weight reflector can be used without riskingdeformation of the reflector during operation.

FIG. 10 b shows a rear perspective view of the reflector and armassembly. Supporting members 377 that provide structural rigidity to thereflector 326 are minimized to reduce weight of the overall structurethat must be moved. A circular fulcrum engaging member 394 is molded onmounting clip 382. Upper spring engaging post 398 is also coupled tomounting clip 382. An extension of the arm 376 forms lower fulcrumengaging end 392. Lower spring mounting posts 396 are also evident.

FIG. 10 c shows a perspective view of the fulcrum mounting post 390. Afulcrum mounting post defines an upper circular fulcrum 391 and a lowerchannel fulcrum 393. This fulcrum arrangement prevents lateral shiftingof the reflector 326 and ensures a clean pivot side to side. The fulcrumdefines a true pivot point with minimal frictional engagement. Mountingthe magnetic drive below and in front of the reflector to be moved,permits a more compact finished system.

FIG. 11 is a perspective view of a projection subassembly of oneembodiment of the invention. A parabolic reflector 524 is coupled to adrive shaft of motor 550. Also coupled along the drive shaft of themotor are plurality of sensor blades which interrupt an optical sensor554 to indicate positioning of the parabolic reflector 524 duringrotation. The motor shaft is positioned to be aligned with the lightsource 522 such that a linear extension of the motor shaft wouldintercept the light source 522. The parabolic reflector 524 as mountedon the shaft slightly off center. However, the tilt of the parabolicreflector 524 as mounted ensures that a focal line of the reflectorintersects the light source 522 throughout the rotation. The rim 526 ofreflector 524 is counterbalanced to provide for smooth rotation of theparabolic reflector 524. Fan blades 556 may be coupled to the rim 526 toassist in the evacuation of heat generated by the light source 522.

The parabolic reflector reflects a light spot from the light source 522onto the projection spreading window 514 which is discussed inconnection with a previously described embodiment has the effect ofspreading the light spot into a vertical light stripe. Because theparabolic reflector is mounted off center as the motor rotates thereflector, the light spot translates through a substantially circularpath on the projection window 514. As a result of the light spreading,the effect in the focal zone, some distance from the projection window,is a light bar sweeping back and forth. In this manner, two gradientsmay be generated and the three dimensional features calculated asdescribed above in connection with other embodiments that sweep thelight stripe through the focal zone.

FIG. 12 a is a sectional perspective view of an inclinometer disposedwithin the camera case. It has been found that a tilt of as little as0.08° will change the imaging characteristics of the ISA where a desiredresolution is 0.1 inches. Inasmuch as table surfaces may often haveslopes greater than this, it is desirable to be able to detect the tiltswith an accuracy of at least 0.80° within the digitizer. Once detected,the slope can be factored out in the rendering of the imaged object onthe host node. The purpose of the inclinometer is to permit adetermination of the amount the digitizer is tilted when resting on asurface. Thus, where the digitizer is placed on an uneven table surface,the inclinometer is used to detect the tilt to permit the subsequentlyrendered image to be compensated for the tilt and resulting distortionin the image captured. Since gravity provides a force having a truedirection independent of the surface tilt, the tilt can be measured offa gravitational orientation unit such as a pendulum, a plum line, aliquid level, etc.

A reflector 306 is disposed on a pendulum 304. The pendulum assemblyrests in fulcrum mount 302 which is coupled to the camera case 220. Themount 302, reflector 306, and pendulum 304 collectively are referred toherein as the inclinometer. The inclinometer is mounted within thecamera case 220, such that regardless of the tilt, no blockage of lens320 occurs. Since the pendulum 304 will hang true vertical, regardlessof the tilt of the table, by appropriately shining a light on thereflector 306 disposed on the pendulum 304, the light is reflected to apoint on the ISA (not shown), and where the light strikes indicates thetilt in the direction the turntable is facing.

FIG. 12 b is a perspective view of the inclinometer positioned relativeto the image sensing array. The LED 308 is disposed on circuit board 258to shine on the reflector of the inclinometer. This light is thenreflected to the ISA 300. Because the fulcrum mount 302 has very lowfriction, the settling time of the pendulum is very high. Very lowfriction is desirable because it is desired that very small changes intilt result in movement of the pendulum 304. Unfortunately, due to thislong settling time, a single measurement of the reflected light may beat significant variance from the actual tilt by virtue of the swingingof the pendulum. Various ways exist to account for this in determiningtilt. One is to take the maximum and minimum as the pendulum swingsthrough its arc and average those. A second way would be to integrateover, for example, 20 seconds. Either method allows the inclinometer inconjunction with the ISA to determine to a high degree of accuracy thetilt to which the digitizer is subjected.

While the pendulum only determines a tilt in a single direction, becausethe upper unit of the digitizer can rotate, it can rotate by, forexample, 90° and determine the tilt in the second direction, therebydetermining the tilt in a second direction, and accordingly determiningthe combined tilt in an X and Y direction for the surface on which it isplaced.

FIG. 13 a is a schematic diagram of a system of one embodiment of theinvention at first mode of operation. In normal mode of operation asshown in FIG. 12 a, ISA 400 is a focal line that can image an objectbetween a minimum distance and a maximum distance perpendicularly from alens 420. The minimum and maximum distance at which the ISA can focusdictate the maximum dimension of an object that can be imaged. It alsodictates the width that the light provided by light source 422 must bewhen it reaches the focal zone. In a typical embodiment, the minimumdistance might be four feet, and the maximum distance might be eightfeet. This yields the maximum cross-dimension for the object of fourfeet. However, when imaging small objects, for example, the size of apenny, imaging at a distance of four feet is unlikely to yield anacceptable imaging result.

FIG. 13 b shows a schematic diagram of a macro lens solution to imagingsmall objects in one embodiment of the invention. By interposing anadditional lens 424 and a wedge prism 426 along the focal line of ISA400, the focal line is bent to intersect the projected light at a pointcloser to the digitizer. Thus, with the additional magnificationresulting from additional lens 424 and the closer focal zone caused bythe wedge prism 426, significantly smaller objects can be imaged.

FIG. 13 c is a schematic diagram of an alternative macro lens solution.In this embodiment, instead of a wedge prism, a pair of 45° reflectors428 are used to move the focal line to intersect the light beam closerto the digitizer.

FIG. 14 is a perspective view of an imaging assembly of one embodimentof the invention. Camera case 520 is coupled to mounting plate 518 of anupper unit and circuit board 258 on which the ISA (not shown) ismounted. A macro lens 530 is movably coupled to mounting plate 518, suchthat in the first position, it is interposed (as shown) in the focalline of the ISA, and in the second position, it does not impinge on thefocal line of the ISA. It is envisioned that the digitizer may beswitched back and forth in and out of macro mode with a toggle switch,slider, or some other mechanism which causes the macro lens to move fromthe first position to the second position, and vice versa.

FIG. 15 a is a diagram of a lens/aperture assembly of one embodiment ofthe invention. Camera case 620 is mounted to enclose the ISA of any ofthe various embodiments of the invention. A camera portal 660 providesan optical path from the ISA to the outside world. In some embodimentsof the invention the camera portal 660 may include a lens barrel.Lens/aperture assembly 640 holds a plurality of lens/aperturecombinations 642, 644, 646. The lens/aperture assembly 640 includes atoothed wheel mounted on a shaft 656 and biased by bias spring 654 forstability. Stepper motor 650 drives the toothed wheel via drive gear652. The lens/aperture combinations, in one embodiment, may each bedistinct lens barrels. In another embodiment the lens/aperturecombination may merely be a lens and aperture to add on to an existinglens barrel for the ISA. In the second case, one of the locations on thewheel such as 642 may have no lens and provide a large enough apertureso that it does not impinge on the existing lens barrel. While threelens/aperture combinations are shown, more or fewer may be provided.

Additionally, it is within the scope and contemplation of the inventionto have apertures and lenses on distinct wheels so that each aperturecan be applied with each lens to yield a larger number of possiblelens/aperture combinations. One embodiment has three possiblecombinations, one for distant three-dimensional imaging, one for distanttwo-dimensional imaging and one for close-up two- and three-dimensionalimaging. In one embodiment, the selection of the lens/aperturecombination may be based on input from a user at a host. Once the useridentifies the conditions, e.g., desired focal distance, the correctlens/aperture assembly is positioned by the system automatically. Inanother embodiment, the digitizer itself identifies the correctlens/aperture combination in the course of its acquisition of theorientation fixture. For example, if the digitizer sweeps looking forthe turntable using the distance three-dimensional lens and does notfind the turntable, it may then transition to the close-upthree-dimensional lens/apparatus combination and sweep again. If theturntable is then found, the close-up combination is selected. Inanother example, the digitizer may sweep looking for the turntable andthen select a correct combination for the turntable at the distance itis found. It should be understood that this is merely illustrative andother methods of lens/aperture combination selection are within thescope and contemplation of the invention.

FIG. 15 b is an exploded view of the assembly of FIG. 14 a. Cameraportal 660 is shown along with positioning posts 670. Positioning posts670 engage recesses 672 in the back surface of lens/aperture assembly640. In this manner proper alignment of the lens/aperture combinationover the camera portal 660 is assured. When a transition betweenlens/aperture combination is desired, the stepper motor 650 drives thewheel to approximately align the desired lens. The bias spring (notshown) biases the recesses 672 over the posts 670 such that the desiredconsistent alignment is achieved. In this manner because the alignmentwill be consistent from one use of the lens/aperture combination to thenext, an initial calibration will compensate for any deviation caused bymanufacturing tolerances.

A majority of the discussion above has been related to scanning anobject rotated by a turntable some distance from the scanner, or in thealternative, a two-dimensional scan (of an object that is not rotated).However, the same digitizer configuration can be used to, for example,image a room from the inside creating a panoramic three-dimensionalview. For example, by setting the digitizer near the center of the roomand allowing it to rotate somewhat more than 360° while scanning, itwill image its surroundings. It is then a software matter for the hostto reconstruct the room.

In another mode of operation, the system may be used in a modifiedstereographic image techniques. The system uses the turntable under thedigitizer control to present two aspects of the object to thedigitizers. By capturing two dimensional images of both aspects usingthe ISA described above, two very high resolution pictures are created.These pictures may then be used to construct a three-dimensional imagefollowing known stereoscopic techniques. In some cases, it may bedesirable to use multiple image capture techniques to ensure the bestpossible resulting image. Thus, for example, the digitizer may capturethe target object using the earlier described intensity gradient basedimaging and then also capture the image in a stereoscopic mode. Bycomparing and/or averaging the resulting images, certain anomaliesresulting from either technique alone may be eliminated.

It is desirable that the upper unit not be permitted to rotateindefinitely in one direction, as such rotation could cause damage tothe connecting cables and create additional stresses in the systemdegrading the system's longevity. However, a hard stop is not feasible,because that would prevent the rotation of greater than 360° which isrequired to ensure a good matchup of a 360° panoramic image. Onesolution to this is to provide a stop which shifts in, for example, a30° arc but has hard stops on the extremes of that arc. In this manner,the digitizer can rotate clockwise until the shifting stop reaches itshard stop at the far edge of the 30° arc. Then scanning can begin in acounter-clockwise direction and continue until the sliding stop has beenpushed back across its 30° arc to the opposite side hard stop. In thismanner, the digitizer can scan a 390° arc. Larger and smaller arc stopsare within the scope and contemplation of the invention.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. In some cases, certainsubassemblies are only described in detail with one such embodiment.Nevertheless, it is recognized and intended that such subassemblies maybe used in other embodiments of the invention. It will also be evidentthat various modifications and changes can be made to the specificembodiments described without departing from the broader spirit andscope of the invention as set forth in the appended claims. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

1. A method comprising: capturing a first two-dimensional image of anobject; causing a relative motion between the object and a field of viewof a capturing device to expose a different aspect of the object to thecapturing device; capturing a second two-dimensional image of theobject; deriving a first three-dimensional digital representation of theobject from the first and second two-dimensional images; creating asecond three-dimensional digital representation by an alternativemethod; capturing with the capturing device an intensity gradient basedthree-dimensional representation of the object.
 2. The method of claim 1further comprising: automatically combining elements of the firstthree-dimensional digital representation with elements of the secondthree-dimensional digital representation to improve quality.
 3. A methodcomprising: capturing a first two-dimensional image of an object;causing a relative motion between the object and a field of view of acapturing device to expose a different aspect of the object to thecapturing device; capturing a second two-dimensional image of theobject; deriving a first three-dimensional digital representation of theobject from the first and second two-dimensional images; creating asecond three-dimensional digital representation by an alternativemethod; capturing with the capturing device an intensity gradient basedthree-dimensional representation of the object; and wherein thecapturing device comprises a linear image sensing array.
 4. A methodcomprising: capturing a first three-dimensional digital representationof a portion of an object using intensity gradient ranging; capturing asecond three-dimensional digital representation of a portion of theobject using stereoscopy; and automatically combining elements from thefirst and second three-dimensional digital representations to improvequality.
 5. The method of claim 4 wherein at least the first capturemethod uses active ranging and at least the second capture method usespassive imaging.
 6. The method of claim 4 wherein the capturing of thefirst three dimensional digital representation and the second threedimensional digital representation is performed using a same imagesensing array (ISA).
 7. The method of claim 4 wherein one of the capturemethods is stereoscopy.
 8. An apparatus comprising: a digitizer capableof using any of at least two capture methods to capture athree-dimensional digital representation of at least a portion of anobject, wherein a first capture method is intensity gradient ranging andwherein a second capture method is stereoscopy.
 9. The apparatus ofclaim 8 further comprising: a processor to automatically combineelements from three-dimensional digital representations captured with atleast two captured methods to improve quality.
 10. The apparatus ofclaim 8 wherein the digitizer is capable of performing at least twocapture methods using a same image sensing array (ISA).
 11. Theapparatus of claim 8 wherein the digitizer comprises: an image sensorarray (ISA) to capture three-dimensional data about an object; alens/aperture assembly having a plurality of lens/aperture combinations;and a controller to automatically select a suitable lens/aperturecombination.
 12. The apparatus of claim 11 wherein each lens/aperturecombination is an independent component.
 13. An apparatus comprising: adigitizer capable of using any of at least two capture methods tocapture a three-dimensional digital representation of at least a portionof an object, the digitizer including; an image sensing array (ISA) tocapture image data in a first mode and tilt data in a second mode; and agravitational orientation unit (GOU) responsive to a relativeorientation of gravity to alter light falling on the ISA in relation tothe relative orientation of gravity.
 14. The apparatus of claim 13wherein at least a first capture method uses active ranging and at leasta second capture method uses passive imaging.
 15. The apparatus of claim13 wherein the GOU comprises: a pendulum having a reflective elementmounted thereon.
 16. The apparatus of claim 15 further comprising: alight emitting diode (LED) mounted to cast light on the reflectiveelement when the LED is on.
 17. An apparatus comprising: a digitizercapable of using any of at least two capture methods to capture athree-dimensional digital representation of at least a portion of anobject wherein the digitizer includes; a shaft; a housing; a bearingcoupled to the housing to rotate the housing relative to the shaft; animage sensing array (ISA) coupled to the housing; and a spring to biasthe shaft relative to the housing, such that successive captures by theimage sensing array are consistently aligned with respect to oneanother.
 18. The apparatus of claim 17 comprising a bias spring alongeach bearing axis having a tolerance above a threshold.